program Square;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  x1, x2, x3, y1, y2, y3, dS : Integer;
  fin : TextFile;

begin
  AssignFile(fin, 'input.txt');
  Reset (fin);
  readln (fin, x1, y1);
  readln (fin, x2, y2);
  readln (fin, x3, y3);
  dS:= abs((x1-x3)*(y2-y3)-(x2-x3)*(y1-y3));
  writeln (dS);
  readln;
  CloseFile (fin);
end.
